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rail-to-rail folded cascode opamp

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Hi ,

I am working on Folded cascode opamp .... I would like to know the differences between two-stage and folded cascode opamp .... Please suggest some good materials and books on folded-cascode opamps

Can any one help in this regard?
 

Hi,
In a telescopic cascode opamp you have a cascode architecture; that is if you have an NMOS common source first, you have an NMOS common gate after that in the signal path.
A folded cascode opamp is called to the stage that you have for example an NMOS common source and a PMOS common gate.
In these two cases there is just one high-impedance node in the circuit.
In a two stage opamp there are two high-impedance nodes in the circuit; that is you add a common source after the cascode (telescopic or folded) stage.
You can refer to Gray book or Razavi book for more information.
 
Generally, the two stage opamp maybe need compensation, because it has two high-impedance nodes as naalald said, and the folded cascode opamp does not , may be the book <analog design essential> written by W.Sansen will be better for you to study
 
the first is one order while the second is 2 order
 

I have gone through the Analog Design Essentials by Sansen.... folded cascode amplifiers are well explained in that ..... Thanks
 

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